1. Field of the Invention
The present invention relates to a segment type color liquid crystal display device which displays predetermined characters and graphics etc. in color.
2. Description of the Prior Art
FIG. 1 is a cross sectional diagram of the prior art segment type color liquid crystal display device 1. A color filter 5 is provided by a printing process or an electrodeposition color process etc. across nearly the entire surface of one side of the transparent substrate 4a, and a plurality of segment electrodes 6 are formed on predetermined display areas of the color filter 5. As shown in FIG. 2, the color filter 5 is composed of red filters R, green filters G, and blue filters B, each of which are formed in narrow strips. The filters R, G, and B are each formed in the areas CF, and for example, black light-blocking layers are formed in the areas SP.
The segment electrodes 6 are composed of electrodes for red, electrodes for green, and electrodes for blue, which correspond to the red filters R, green filters G, and blue filters B respectively. An orientation film 7a is formed on the surface of the transparent substrate 4a where the color filter 5 and the segment electrodes 6 are formed.
A plurality of common electrodes 8 are formed on the surface of one side of the transparent substrate 4b, across the areas which include the segment electrodes 6, and further, an orientation film 7b is formed on that surface. The transparent substrates 4a and 4b are arranged so that the surface on which the respective orientation films 7a and 7b are formed face each other. A twisted nematic liquid crystal layer 9 is sandwiched between the transparent substrates 4a and 4b, and is sealed with a sealant 10. Further, the polarizer plates 11 and 12 are provided on the surfaces of the transparent substrates 4a and 4b respectively which are on the sides opposite from the liquid crystal layer 9.
Here, the polarizer plates 11 and 12 are arranged so as to achieve parallel polarization, and when voltage is not applied, light is allowed to pass through the color liquid crystal display device 1, performing so-called normally white display. Normally white display is a display method wherein the background is for example white in color, and which displays the desired configuration by applying voltage to the liquid crystal layer 9 corresponding to the configuration to be displayed, thereby changing the light distribution state of the molecules in the liquid crystal and blocking the light. In the color liquid crystal display device 1, color filter 5 is formed by the minute rectangular shaped filters R, G, and B as shown in FIG. 2, and the transmitted light turns white due to the mixing of red light, green light, and blue light. In other words, when voltage is not applied, white is displayed as the background color in the color liquid crystal display device 1. Therefore, in case for example, voltage is applied only to the electrodes for blue which make up the segment electrodes 6, the blue light is blocked and yellow is displayed due to the mixing of red light and green light.
When the above mentioned color liquid crystal display device 1 is used in audio devices, OA (Office Automation) devices, or home electrical products, there are cases where a transparent film preprinted with numbers, characters and graphics etc. is arranged on the front of the color liquid crystal display device 1. For example, when using the color liquid crystal display device 1 as a level meter for a cassette tape recorder, characters and graphics such as the characters "R" and "L" indicating the left and right channels, and the numbers indicating the recording playback level, which need not be displayed using the color liquid crystal display device 1, that is to say the characters and graphics etc. which may always be in a visible state, are printed on a transparent film and arranged on the front of the color liquid crystal display device 1.
Then, when the characters etc. printed on the transparent filter were small, the periphery of the characters appeared blurred and sometimes difficult to distinguish, because the color filter 5 as mentioned above, was composed of a plurality of filters formed in minute rectangular shapes arranged, for example, in a matrix, and hence there was a limit on the size of the characters.
For example in FIG. 2, let us imagine a case where part of a character is arranged in area AO. The color filter 5 has the 3 types of color filter R, G and B as 1 unit area, and in this 1 unit area, white color is obtained by the mixing of the transmitted light. However, in area A1 only red light is transmitted, and sometimes area AO which is close to area A1 appears to be colored red and blurred. Further, in areas A2 and A4 green light is transmitted, and sometimes area AO which is close to areas A2 and A4 appears to be colored green and blurred. Still further, in area A3 only blue light is transmitted, and sometimes area Ao which is close to area A3 appears to be colored blue and blurred. That is to say, the phenomenon in which the periphery of a character appears blurred occurs because the color balance of the transmitted light breaks down.